I've compiled a list of all of the directories for New York City and surrounding environs and put them on my blog. Once you get past the 1840's, you have a lot more consistent coverage.
I draw upon four main sources:
1. New York Public Library collection
2. Google Books
3. Internet Archive
4. A set of direct PDF links from latinamericanstudies.org.
5. The Brooklyn Public Library's online collection of Brooklyn directories.
Using city directories can be extremely useful when you have a name but not a business, or if you're trying to figure out if Person X was still a partner with Person Y on this date.
The directories stretch from 1786, and I take it up to 1910 since I'm primarily interested in steel pens.
The full link is: https://thesteelpen.com/2017/11/15/research-resources-new-york-city/
If anyone has a link I haven't included or knows of an online archive I can add, let me know.